In typical motorcycles having a chain or belt drive, the pinion, which drives the chain or the drive belt, is typically situated at least approximately 65 mm offset in relation to the axis to which the rear wheel swing arm is linked. The clutch is commonly situated on the transmission input shaft in typical motorcycles. Seen in a side view of the motorcycle, the clutch thus “overlaps” the transmission output shaft. In the following, the transmission output shaft is understood as the shaft on which the pinion is situated, which drives the chain or the belt, which in turn drives the rear wheel. The transmission output shaft is typically located in front of the swing arm axis.
Typical motorcycle concepts of this type have a whole array of disadvantages. Because of the offset between the chain pinion and the swing arm axis, a certain chain sag is necessary. In particular for off-road motorcycles, which have a spring range of 150 mm or more, a significant chain sag is required. In a motorcycle having a spring range of 300 mm, for example, a chain sag of approximately 70 mm is required.
A greater chain sag results in relatively strong friction losses and requires a special chain guide. Greater chain wear also results with a large chain sag. A further result of the large chain sag may be strong running noises due to “chain whipping.” “Encapsulation” of the chain is constructively complex, in particular in the event of large chain sag.
A further problem of typical motorcycle concepts may be seen in that the pinion diameter is limited in relation to the swing arm mounting by the clearance required for a pivot movement of the swing arm. Furthermore, it is problematic that the swing arm spar is situated adjacent to or below the driving strand of the chain, which implies a relatively large gauge of the swing arm spars and, in the case of a single-arm swing arm, makes the construction very complex, because the engine housing and the swing arm mounting must also be housed having an offset in relation to the transmission output shaft between the rear wheel and the output shaft of the transmission. Because in typical motorcycles, the swing arm spars must always lie between the top and bottom chain strands, the bottom spring strut attachment is located at a relatively low level, which in turn has an unfavorable effect on the spring strut progression.
As already noted, the clutch is typically situated on the transmission input shaft in normal motorcycles. Quite high torques occur on the transmission input shaft. To be able to transmit these high torques continuously, the clutch must be relatively large or run in an oil bath. Oil-bath clutches have the disadvantage that they may result in a relatively rapid contamination of the oil.
In normal motorcycles, the frame is also typically designed relatively complexly. The frame connection between the steering head and the swing arm axis lying behind the transmission output shaft must be guided past the clutch basket, which has a relatively large construction. In typical motorcycles, in which the swing arm axis is situated behind the drive pinion, the frame typically has frame tubes which extend below the engine past the clutch housing to the swing arm linkage points. Frame constructions of this type imply an unfavorable force flow and are also relatively heavy and costly to produce. The engine mounting is also relatively difficult with frames of this type, because the engine and the transmission are “embedded” very tightly in the frame.
It was already recognized many decades ago that it would be advantageous if the drive pinion which is provided for driving the chain or the drive belt was situated coaxially to the swing arm axis. Concept approaches are described, for example, in U.S. Pat. No. 6,755,272 B2, GB 558 387, FR 2370 625, WO 02/094649 A1, or EP 592 655 B1. However, in the motorcycles described therein, the drive pinion is not seated on the transmission output shaft, but rather on a separate shaft which is driven by the transmission output shaft via a chain or belt drive. This is a relatively cumbersome design and has therefore also not been successful.
In the textbook “Motorradtechnik [Motorcycle Technology],” 5th edition, Vieweg-Verlag, ATZ MTZ-Fachbuch, pages 295-298, edited by Jürgen Stoffregen, the basic idea of situating in the chain pinion coaxially to the pivot axis is also described. However, Stoffregen does not provide a concrete description of how the chain pinion may be driven and how the chain pinion is to be situated in relation to the transmission.
FR 1038 140 may also be included in the technical background.
The object of the present invention is to provide a completely novel vehicle concept which may be implemented in a simple design, which allows the problems described at the beginning to be avoided, as well as providing an engine/transmission unit as a basis for such a vehicle.
The starting point of the present invention is the consideration of providing a novel engine/transmission unit, which allows a correspondingly novel vehicle concept, in particular a novel motorcycle concept. Such an engine/transmission unit has an engine having a crankshaft which extends transversely to the travel direction of the vehicle, as well as a transmission and a clutch which may assume an open state and a closed state, the clutch allowing a torque transmission from the crankshaft to the transmission in the closed state. A central feature of this novel engine/transmission unit is that the clutch is situated coaxially to the crankshaft. The rotational axis around which the clutch disks rotate is thus transverse to the travel direction of the vehicle or the motorcycle.
The advantage results due to the coaxial configuration of crankshaft and clutch that the clutch-in contrast to typical vehicle engine/transmission units, in which the clutch is typically situated on the transmission input shaft-operates at higher speeds and lower torques and may thus be implemented more compactly. The clutch may thus have a comparatively small diameter, which in turn has the advantage that it does not extend up into the area of the transmission output shaft. The reason why this is so advantageous in regard to the overall vehicle concept will be explained in greater detail below.
It is expressly noted that the present invention is not restricted to the use of such an engine/transmission unit in motorcycles, but rather is applicable very generally in connection with vehicles. The following description and the claims are also to comprise multiwheel vehicles in addition to motorcycles, such as three-wheeled vehicles or four-wheeled vehicles, in particular so-called “quads.”
According to a refinement of the present invention, the vehicle has a frame and a rear wheel swing arm, which is situated so it is pivotable on a swing arm axis in relation to the frame, and a transmission having a transmission housing and a transmission output shaft projecting out of the transmission housing. A “transmission output pinion” is situated on the transmission output shaft, which is coupled to a chain wheel, which drives a rear wheel or rear wheels of the vehicle situated in the rear wheel area of the vehicle via a traction mechanism, such as a chain or a toothed belt.
According to a refinement of the present invention, the transmission output pinion situated on the transmission output shaft is situated coaxially to the swing arm axis. A coaxial configuration of the transmission output pinion, i.e., the pinion which drives the chain or the belt, and the swing arm axis has the advantage that practically no sag of the “traction mechanism,” i.e., the drive chain or the drive belt, has to be maintained for the spring compression of the rear wheel swing arm, as is the case for typical motorcycles having a chain or belt drive. The problems connected with a chain sag are thus avoided from the beginning.
According to a refinement of the present invention, the swing arm axis, i.e., the pivot axis around which the rear wheel swing arm pivots, extends through the transmission/engine housing. When “engine/transmission housing” or “transmission housing” or “engine housing” are discussed in the following, these terms are each to be understood broadly. The terms “engine/transmission housing” or “transmission housing” or “engine housing” are to be understood very generally in the following description and in the patent claims as the housing of the transmission and/or the housing of the engine.
The swing arm axis extending through the transmission housing projects out of the transmission housing on opposite sides of the transmission housing. Ends of the swing arm axis may then be mounted in the frame of the vehicles so they are pivotable. The swing arm axis may be mounted in the frame by roller bearings or friction bearings. For example, taper roller bearings may be used for mounting the swing arm axis in the frame. The taper roller bearings may be situated in an O configuration, for example.
It is expressly noted that the swing arm does not necessarily have to be mounted in the frame. The swing arm may also be mounted to or on the transmission output shaft using bearings, e.g., needle bearings, if the transmission output shaft and the engine/transmission housing are implemented as sufficiently stable to support the forces introduced via the swing arm.
The rear wheel swing arm may be permanently connected to the swing arm axis. A simple possibility is to clamp the rear wheel swing arm to the swing arm axis using a clamp connection.
The transmission output shaft on which the transmission output pinion is situated is preferably mounted in the transmission housing by roller bearings.
According to a refinement of the present invention, the transmission output shaft is implemented as a hollow shaft. This has the advantage that the swing arm axis may be inserted very simply through the transmission output shaft, which allows very simple mounting and dismounting of the rear wheel swing arm.
As already noted, the engine/transmission unit may be installed in a vehicle in such a way that the crankshaft of the engine extends in a transverse direction, i.e., parallel to the swing arm axis of the vehicle. In contrast to most normal vehicles and/or motorcycles, in which the clutch is situated on the transmission input shaft, according to the present invention, the clutch is situated coaxially to the crankshaft and preferably on the crankshaft itself. Because higher speeds and smaller torques arise on the crankshaft than on the transmission output shaft, the clutch may be implemented smaller, i.e., having a smaller diameter, than in typical motorcycles.
In typical motorcycles, in which the clutch is situated on the transmission input shaft, the clutch overlaps the transmission output shaft seen in a side view of the vehicle. In typical motorcycles, a coaxial configuration of swing arm axis and transmission output pinion would not be possible at all, because the swing arm axis would penetrate the clutch.
In contrast, a configuration of the clutch on the crankshaft has the advantage that the clutch may be implemented more compactly and, seen in a side view of the vehicle, the clutch does not overlap the transmission output shaft and thus allows “through insertion” of the swing arm axis. Because smaller torques arise on the crankshaft than on the transmission input shaft, different types of clutches may be used, e.g., single-disk clutches, multiple disk clutches, dry clutches, wet clutches, etc.
A “drive element” of the clutch is preferably connected rotationally fixed to the crankshaft. An “output element” of the clutch is situated so it is rotatable in relation to the crankshaft and is connected to a primary pinion which is mounted so it is rotatable on the crankshaft. The output element may be a clutch basket which may be connected in one piece to the primary pinion. Alternatively thereto, the clutch basket and the primary pinion may also be implemented in two pieces. The primary pinion may be mounted on the crankshaft using a roller bearing or a friction bearing. The primary pinion is preferably mounted on the crankshaft using a needle bearing.
The torque may be transmitted from the primary pinion seated on the crankshaft via an intermediate wheel situated on an intermediate shaft to the transmission input shaft. The intermediate wheel or another gearwheel seated on the intermediate shaft engages with a gearwheel of the transmission input shaft, which is situated offset in relation to the intermediate shaft in the direction of the rear wheel swing arm. Multiple shiftable gearwheel stages which are permanently engaged are situated adjacent to one another on the transmission input shaft and on the transmission output shaft, via which the individual gears of the transmission may be engaged.
The basic principle of the present invention described above also allows, in contrast to the prior art, an optimum design of the frame, in particular an optimum design of the motorcycle frame in the case of a motorcycle.
According to a refinement of the present invention, the frame has at least two left and two right frame tubes. The left frame tubes are essentially mirror-identical to the right frame tubes. The frame tubes of each frame side intersect one another. “Intersect” in this context means that they run together and are connected to one another. The frame is preferably designed in such a way that the swing arm axis extends through the “intersection point” of the left frame tubes and through the intersection point of the right frame tubes. The engine and the transmission of the vehicle may be situated in the area between the left and the right frame tubes.
The left and the right frame tubes may each be differentiated by terms into a left and a right bottom frame tube and a left and a right top frame tube. Seen in a side view of the vehicle, the two bottom frame tubes may be essentially linear and extend forward up into an area below handlebars of the vehicle from the swing arm axis and be connected there to a steering head bearing tube. In a top view of the vehicle, the two bottom frame tubes are not necessarily linear, but rather may also be curved.
The two top frame tubes are situated above the bottom frame tubes and extend from an area below the handlebars or from a steering head bearing tube backward down to the pivot axis.
A frame designed in this way has multiple advantages. The engine, the transmission, and a radiator of the motorcycle may be inserted from below as a prefinished assembly into the area between the left and the right frame tubes, which significantly simplifies the mounting and/or dismounting.
While in typical motorcycles having a chain drive the frame tubes extend from the handlebars area below the engine and/or the transmission to the swing arm bearing of the rear wheel swing arm, according to the present invention, the left and the right frame tubes of the frame run laterally past the engine and/or the transmission from the handlebars area diagonally downward to the swing arm axis. This has the advantage in turn that a continuous radiator may be situated in an area below the bottom frame tubes and forward of the engine.
An air filter of the engine may be situated in a very space-saving way which is protected from sprayed water in the area proximal to the handlebars between the top and bottom frame tubes above the engine.
An onboard battery of the motorcycle may be situated in an area proximal to the swing arm axis between the top and bottom frame tubes above the transmission. The center of gravity of the vehicle is preferably located in this area. Situating the relatively heavy onboard battery in the area of the center of gravity of the vehicle very significantly improves the handling of the vehicle.
The frame described above also has significant advantages in regard to the configuration of a spring strut. The spring strut may be situated between the frame and the rear axle swing arm. It has the object of springing and damping movements of the spring strut occurring during travel. A bottom end of the spring strut may be connected in an articulated way to the swing arm. A top end of the spring strut may be connected in an articulated way to the frame. The spring strut extends from bottom rear diagonally to top forward.
In the frame design described above, it is advantageous to situate the spring strut in such a way that, seen in a side view of the motorcycle, it is in an essentially linear extension of the forward sections of the top two frame tubes. In a configuration of this type, the forces exerted by the spring strut on the frame are essentially introduced into the frame in the longitudinal direction of the forward sections of the top frame tubes. The top frame tubes function as “compression bars” and are primarily loaded with pressure and only slightly with bending upon spring compression of the rear wheel swing arm. In contrast to typical motorcycles, the frame thus allows a significantly flatter installation of the spring strut supports, which allows a high progression during spring compression of the spring strut.
The fuel tank may also be situated in a more favorable position closer to the center of gravity in the vehicle concept described above than is the case in most normal vehicles and/or motorcycles. According to a refinement of the present invention, the fuel tank is situated in an area above the spring strut and below the seat of the vehicle. The tank cover of the fuel tank may be situated on the top side of the fuel tank below the seat. The seat then only has to be removed for filling. In comparison to typical motorcycles, in which the fuel tank is situated forward of the seat, a configuration in the area above the spring strut has the advantage that the center of gravity of the vehicle may thus be lowered, which further improves the handling.
Alternatively thereto, an access opening or a “hole” may also be provided in the seat, via which the tank connecting piece of the fuel tank is accessible. Filling is then also possible without removing the seat.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.